Hello
Using a MacBook Pro Intel with macOS 12.7.6 Monterey, I test in Objective-C an event for the option key but it is not working
- (void)keyDown:(NSEvent *)event {
printf("%s %p\n", __FUNCTION__, self);
BOOL altFlag = [event modifierFlags] & NSEventModifierFlagOption;
if (altFlag) {
// UpdateClass
printf("option pressed\n");
} else {
printf("option not pressed\n");
}
}
The same in Swift works fine
override func keyDown(with event: NSEvent) {
if event.modifierFlags.contains(.option) {
print("option pressed")
} else {
print("option NOT pressed")
}
}
The Obj-C code works fine on a MacBook Air Tahoe 26.3
Any idea why it does not work on the macOS 12.7.6 Intel?
Many Thanks Jean
Try re-expressing your condition as
([event modifierFlags] & NSEventModifierFlagOption) != 0
This is a behavior with BOOL and bitmasks that catches a lot of people by surprise. What’s happening here is that your bitwise operation is producing a NSEventModifierFlags value that is a single bit at 1 << 19, and then that value is being implicitly coerced into a BOOL.
The definition of BOOL varies by platform and architecture; on modern targets it’s a C99 bool, but on older targets it is a char. (Search up the OBJC_BOOL_IS_BOOL preprocessor define for more information.)
When your bitmask result is implicitly cast into a char, it is truncated to the lowest order byte which is all zeroes. You can avoid this by doing a test that produces a boolean result, like != 0.
